Non-attached tire monitoring device

ABSTRACT

A non-attached monitoring device includes monitoring assembly and an antenna configured to radiate signals from the monitoring assembly. The antenna is configured to radiate through the oriented attenuating body of the tire sidewall regardless of the position of the monitoring device with respect to the tire sidewall. In one embodiment, the antenna has a body that is looped back on itself. The body may be parallel to or perpendicular to the antenna ground plane. In another embodiment, a radiating slot antenna is configured to provide transmissions through the tire sidewall regardless of the position of the monitoring device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Patent Application Ser. No.60/445,074 filed Feb. 4, 2003; the disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to non-attached monitoringdevices and antenna configurations for transmitting through an orientedattenuating body. More particularly, the present invention is related toa non-attached monitoring device that is free to move about within thecavity formed by the tire and the rim on which the tire is mounted.Specifically, the present invention relates to the configuration of thedevice antenna and its ability to transmit data through the attenuatingbody of the tire sidewall.

2. Background Information

Monitoring conditions of pneumatic tires while they are installed and inuse on a particular vehicle is desired in the art. The users of thistechnology particularly desire to measure the internal temperature andinternal pressure of a tire. These non-destructive measurements arepreferably taken while the tire is in use without having to remove thetire from the vehicle or otherwise interrupt the use of the vehicle totake the measurements. It is particularly desirable to monitor theconditions and statistics of large off-the-road truck tires because theoff-the-road tires are expensive and subject to harsher conditions thantypical passenger car tires. Owners of highway trucks also desire tomonitor their tires. Both types of tires must be regularly maintained tomaximize vehicle usage and tire efficiency.

Numerous types of monitoring devices are known in the art. One type ofknown monitoring device uses a passive integrated circuit embeddedwithin the body of the tire that is activated by a radio frequencytransmission that energizes the circuit by inductive magnetic coupling.Other prior art devices used for monitoring tire conditions includeself-powered circuits that are positioned external of the tire, such asat the valve stem. Other active, self-powered programmable electronicdevices are disclosed in U.S. Pat. Nos. 5,500,065, 5,573,610, 5,562,787,and 5,573,611 which are assigned to the Assignee of the presentapplication.

The prior art attachment problems exist because the forces on anelectronic monitoring device while connected to a pneumatic tire aresignificant and numerous. The forces in the footprint area of the tiremust be considered when mounting a monitoring device. Tires are subjectto rotational forces when the vehicle is moving and also to variousimpact forces when the tire contacts surface irregularities. The tirewill also deform and deflect during maneuvering because the loads to thewheel change. The attachment of the monitoring device to the tire mustbe strong enough and secure enough to maintain the position of themonitoring device with respect to the tire while experiencing all ofthese forces while also protecting the monitoring device from damageresulting from these forces. These concerns have lead to the use ofnon-attached monitoring devices such as those disclosed in U.S. Pat. No.6,082,192 (commonly assigned) and U.S. Pat. No. 4,067,235.

One drawback with these devices is that their freedom of movementprevents the position of the antenna from being accurately predictedwhile the monitoring device is in use. The art recognizes that theposition of the antenna with respect to the tire sidewall is animportant factor when attempting to radiate a radio frequency signalthrough certain tire sidewall constructions. The rubber compositematerials used in tire constructions may include a conductive materialsuch as carbon black. These materials can attenuate the signal of someradio frequency transmissions through the tire sidewall or other tirestructure. Some tire constructions such as those commonly used incertain highway truck tires and off-the-road tires can also includemetal cords. For example, a plurality of metal cords oriented radiallymay be present in the sidewall area of these tires. Such metalstructures will provide additional attenuation of a radio frequencysignal passing through the tire sidewall. The orientation of the metalcords in the tire structure in relation to the orientation of theelectromagnetic field associated with a radio signal passing through thetire sidewall will determine the degree of additional attenuation thatthe presence of the metal cords imparts upon the radio signal.Therefore, a tire structure of this type is termed an “oriented”attenuating body. The electromagnetic field orientation is a directresult of the type and orientation of antenna used in transmitting theradio signal. Certain antenna configurations provide more desirabletransmissibility through the oriented attenuating body than otherantenna configurations. One known antenna configuration is disclosed inU.S. Pat. No. 6,474,380 (commonly assigned) wherein a dipole antenna isfixed to the sidewall and disposed perpendicular to the metal bodycords. This type of antenna configuration is not typically used withnon-attached monitoring devices because the movement of the monitoringdevice does not allow the antenna to remain perpendicular to the metalbody cords during all transmissions. Some prior art solutions haveattempted to control the position of the non-attached monitoring devicewithin the tire so that the antenna would be in a predictable positionwith respect to the tire sidewall. The art desires a monitoring deviceand antenna configuration that will provide signal transmissions throughthe tire sidewall regardless of the position of the monitoring devicewith respect to the tire sidewall.

BRIEF SUMMARY OF THE INVENTION

The invention provides a monitoring device having a monitoring assemblyand an antenna configured to radiate signals from the monitoringassembly. The antenna is configured to successfully radiate asubstantial portion of the radio signal through the oriented attenuatingbody of the tire sidewall regardless of the position of the monitoringdevice with respect to the tire sidewall. In one embodiment, the antennahas a body that is looped back on itself. The body may be parallel to orperpendicular to the antenna ground plane. In another embodiment, theinvention provides an antenna body disposed at an angle between zero and90 with respect to the antenna ground plane.

The invention also provides monitoring device embodiments that each havea different radiating slot antenna configured to provide transmissionsthrough the tire sidewall regardless of the position of the monitoringdevice. The first embodiment uses a single slot formed by a pair ofdisc-shaped conductive surfaces. The second embodiment uses a pair ofslots formed by two pairs of disc-shaped conductive surfaces. The thirdembodiment uses a pair of conductive surfaces that form a serpentineslot at the outer surface of the monitoring device.

The invention also provides an antenna configuration that may bedisposed within the encapsulation layer of the monitoring device orwithin the protective body of the monitoring device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a view of a reader disposed outside a sectioned pneumatic tirewith one embodiment of the monitoring device of the present inventionloosely disposed in the tire.

FIG. 2 is a front elevation view of the first embodiment of themonitoring assembly of the present invention with the protective body ofthe monitoring device shown in section.

FIG. 3 is a side elevation view of the first embodiment of themonitoring assembly.

FIG. 4 is a bottom plan view of the first embodiment of the monitoringassembly.

FIG. 5 is a front elevation view of a second embodiment of themonitoring assembly of the present invention with the protective body ofthe monitoring device shown in section.

FIG. 6 is a side elevation view of the second embodiment of themonitoring assembly.

FIG. 7 is a bottom plan view of the second embodiment of the monitoringassembly.

FIG. 8 is a section view of a third embodiment of the monitoring deviceof the present invention with the monitoring assembly shown inelevation.

FIG. 9 is a perspective view of the antenna used in the third embodimentof the monitoring device of the present invention.

FIG. 10 is a view similar to FIG. 8 showing a fourth embodiment of themonitoring device of the invention.

FIG. 11 is a perspective view of the antenna used in the fourthembodiment of the monitoring device of the present invention.

FIG. 12 is a front elevation view of a fifth embodiment of themonitoring device of the present invention.

FIG. 13 is a side elevation view taken along line 13—13 of FIG. 12.

Similar numbers refer to similar parts throughout the specification.

DETAILED DESCRIPTION OF THE INVENTION

The electronic monitoring device using the antenna configuration of thepresent invention is indicated generally by the numeral 2 in theaccompanying drawings. Monitoring device 2 is loosely disposed within apneumatic tire 4 in FIG. 1 such that the movement of monitoring device 2is only restricted by the body of tire 4 and the rim 6 on which tire 4is mounted. As described above, this type of monitoring device does nothave to be mounted to tire 4 or rim 6. One drawback to the free movementis that the antenna 10 of monitoring device 2 does not maintain aconsistent orientation with respect to tire 4 or rim 6. This is aproblem because tire 2 typically has a sidewall 8 that functions as anattenuating body because sidewall 8 includes a plurality of metal cords9. In the case of tire 2, the attenuating body is oriented. In thecontext of this application, an “oriented” attenuating body will impedesignals of one orientation to a lesser degree than signals of anotherorientation. An oriented attenuating body thus has a minimum attenuatinglevel and a maximum attenuating level depending on the orientation ofthe signal being attenuated by the body. The maximum attenuating levelmay prevent signals from being received by the reader monitoring thetransmissions from the monitoring device. If the orientation of theantenna were fixed with respect to the sidewall, a most favorable oroptimal antenna orientation would exist as well as a least favorableantenna orientation. In a non-attached monitoring device, theorientation of the antenna with respect to the sidewall changes. Priorart monitoring device antennas would thus be positioned in less thanoptimal orientations when used with a non-attached monitoring device.The antennas described below are thus configured to provide a radiosignal orientation capable of successfully passing through sidewall 8regardless of the orientation of device 2 with respect to sidewall 8.The antennas thus provide constant performance independent of theposition of the monitoring device.

FIGS. 2–4 depict a first embodiment of antenna 10 while FIGS. 5–7 depicta second embodiment of antenna 10. Each antenna embodiment 10 isconfigured to provide a transmission pattern having at least one portionthat is not so severely attenuated by sidewall 8 such that a reader 12positioned outside sidewall 8 will receive a signal regardless of theorientation of device 2 with respect to sidewall 8. In some embodiments,the signal received by reader 12 will have a constant strength as device2 tumbles within the chamber of tire 4.

All of the antenna embodiments shown in this application are depicted inuse with an exemplary monitoring assembly 14 having a circuit board 16that is disposed in a circuit board reference plane 18. Reference plane18 is disposed coplanar with the drawing sheet in FIGS. 4 and 7 andperpendicular to the drawing sheet in FIGS. 2, 3, 5, 6, 8, and 10.Monitoring assembly 14 may also include a power source such as thebatteries 20 shown in the drawings. Monitoring assembly 14 furtherincludes the sensors and electronics 22 that are used to measure anengineering condition of tire 4 (such as temperature or pressure) andtransmit data by RF transmission through antenna 10 relating to thecondition to a reader positioned outside tire 4. The specific sensorsand electronics may vary but may be any one of the variousconfigurations known in the art. Exemplary monitoring assemblies arecited above.

For example, monitoring assembly 14 may include one or more microchips,one or more amplifiers, one or more batteries, one or more sensors suchas pressure, temperature, and/or mileage/distance sensors. While notshown in the drawings, it is envisioned that the microchip itself cancontain all or some of the aforementioned components. Assembly 14 may beactive or passive depending on the type of reader and system used.

The first embodiment of antenna 10 has a body 30 disposed substantiallyparallel to reference plane 18. In this embodiment, circuit board 16functions as the ground plane for antenna 10. Body 30 may be disposed inor on circuit board 16 or may be spaced from board 16 as shown in thedrawings. When a spaced configuration is desired, legs 32 are providedwith at least one of the legs 32 electrically connected to theelectronic component that sends the signal to be radiated from antenna10. Legs 32 may also radiate signals in an orientation perpendicular tobody 30. The second embodiment of antenna 10 is shown in FIGS. 5–7wherein body 30 is disposed perpendicular to reference plane 18 as shownin FIG. 6. In other alternative embodiments of the invention, body 30 ofantenna 10 may be disposed at an angle between zero and 90 degrees.

Each body 30 is looped back on itself to create signals of differentorientations that will be attenuated differently by sidewall 8. In oneembodiment, body 30 may only contain a 90 degree arc. In the embodimentsshown in the drawings, body 30 forms at least a half loop that containsa 180 degree arc. The half loop may follow a generally smooth circularpath, a generally smooth oval path, or a wavy path. The signalstransmitted from body 30 are thus disposed at all angles from zero to180 degrees with respect to the ground plane. The 180 degree signalradiation pattern ensures that one area of body 30 will be desirablydisposed (these signals will be attenuated at the minimum attenuationlevel) with respect to sidewall 8 regardless of the orientation ofmonitoring device 2 with respect to sidewall 8. Monitoring device 2 maythus tumble about within tire 4 while still transmitting signals toreader 12 outside of tire 2.

Both antenna embodiments 10 may be contained within the compact body ofmonitoring device 2 because the body 30 is looped back over board 16.Antenna 10 may thus be encapsulated with monitoring assembly 14 insidethe rigid encapsulation material 40 as shown in FIGS. 2–4. This materialmay be a rigid epoxy that protects assembly 14 and antenna 10 fromsignificant bending forces by maintaining their relative positions.Antenna 10 may also extend into the protective body 42 of monitoringdevice 2 as shown in FIGS. 5–7. Exemplary encapsulation layers andexemplary protective bodies are disclosed in U.S. Pat. No. 6,082,192which are incorporated herein by reference.

A third embodiment of the monitoring device of the invention isindicated generally by the numeral 2 in FIG. 8. In this embodiment, theantenna 50 includes a pair of spaced conductive bodies 52 and 54 thatextend through the body of device 2. In this embodiment and in thefollowing embodiments, conductive bodies 52 and 54 may be conductivefoils or conductive coatings disposed on the body portions of device 2.In the exemplary embodiment, each body 52 and 54 is disc-shaped as shownin FIG. 9. In other embodiments, the outer slot defined by theintersection of the bodies 52 and 54 with the outer surface of the bodyof device 2 may be circular while the bodies are curved inside the bodyof device 2. For example, bodies 52 and 54 may be portions of concentricspheres disposed with the body of device 2. Bodies 52 and 54 are spacedapart to form a cavity that extends to the outer surface of the body ofdevice 2 and defines a slot about the equator of device 2. The cavitymay be filled with a dielectric filler material 56. In otherembodiments, the cavity may be left hollow with mechanical spacers usedto maintain the spacing between bodies 52 and 54. The size and spacingof bodies 52 and 54 and the type of material 56 are used to tune antenna50. Bodies 52 and 54 thus divide the body of device 2 into two portions.In the exemplary embodiment, monitoring assembly 14 is shown in onehemisphere such that device 2 would be weighted to stop in a predictableorientation. In other embodiments, the other hemisphere may becounterweighted to balance device 2.

Antenna 50 is fed at the center of one of bodies 52 and 54 while theother body 52 and 54 acts as the ground plane for antenna 50. When fedat its center, antenna 50 will radiate signals from the entirecircumference of the slot. Some portion of the radiated signal will thuspass through sidewall 8 regardless of the orientation of device 2.

A fourth embodiment of the monitoring device of the invention isindicated generally by the numeral 2 in FIG. 10. In this embodiment, theantenna 60 includes a two pairs of spaced conductive bodies 62 and 64that extend through the body of device 2. Bodies 62 and 64 each havefirst and second planar leg portions disposed perpendicular to eachother with the outer edge of each leg being curved. In the exemplaryembodiment, each body 62 and 64 is the shape of the inner surface of aquarter sphere as shown in FIG. 11. Bodies 62 and 64 are spaced apart toform a cavity that extends out of the body of device 2 in a pair ofslots about perpendicular equators of device 2. The cavity may be filledwith a filler material 56. In other embodiments, the cavity may be lefthollow with mechanical spacers used to maintain the spacing betweenbodies 62 and 64. The size and spacing of bodies 62 and 64 and the typeof material 56 are used to tune antenna 60. Bodies 62 and 64 thus dividethe body of device 2 into four portions. In the exemplary embodiment,monitoring assembly 14 and batteries 20 are shown in opposed quadrantssuch that device 2 is evenly weighted. Weights may also be added to theother quadrants if needed.

Antenna 60 is fed at the center of the two opposed bodies 62 while theother bodies 64 function as the ground plane of antenna 60. Antenna 60will radiate signals from the entire circumference of both slots. Someportion of the radiated signals will thus pass through sidewall 8regardless of the orientation of device 2.

A fifth embodiment of the monitoring device of the invention isindicated generally by the numeral 2 in FIGS. 12 and 13. In thisembodiment, the antenna 70 includes a two conductive bodies 72 and 74that extend through the body of device 2. In the exemplary embodiment,each body 62 and 64 forms a serpentine pattern when it ends at the outersurface of device 2. Bodies 72 and 74 are spaced apart to form a cavitythat extends from the center of device 2 out of the body of device 2 ina serpentine slot that extends about the body of device 2 such that atleast two portions of the slot may be viewed in the six possibleelevation views of device 2. The cavity may be filled with a fillermaterial 56. In other embodiments, the cavity may be left hollow withmechanical spacers used to maintain the spacing between bodies 72 and74. The size and spacing of bodies 72 and 74 and the type of material 56are used to tune antenna 70. Bodies 72 and 74 thus divide the body ofdevice 2 into two portions. As above, the monitoring assembly may bedisposed in one or both of the two portions to balance device 2 asdesired.

Antenna 70 is fed at the center of one of the two opposed bodies 72while the other of the two opposed bodies 74 function as the groundplane of antenna 70. Antenna 70 will radiate signals from the entirecircumference of the serpentine slot. Some portion of the radiatedsignals will thus pass through sidewall 8 regardless of the orientationof device 2.

In each of the third, fourth and fifth embodiments, the conductivebodies do not have to extend entirely through the body of the monitoringdevice as shown in the drawings. For example, the conductive bodies maybe configured such that the cavity defined between the bodies is achannel that extends from the slot into the body of the monitoringdevice. In the case of the third embodiment, each conductive body 52 and54 may be in the shape of a flat doughnut or a flat washer (the shapeformed by a reference plane passed through the diameter of a torus).

In the foregoing description, certain terms have been used for brevity,clearness, and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention is anexample and the invention is not limited to the exact details shown ordescribed. For example, the non-attached monitoring device described inthe exemplary embodiment of the invention is used with pneumatic tireshaving attenuating sidewalls. These monitoring devices may also be usedin other applications wherein an attenuating body is disposed betweenthe monitoring device and the reader. Exemplary applications includetypes of silos, freezers, pumps, and pipes.

1. A non-attached monitoring device for monitoring an engineeringcondition of a tire and transmitting data related to the engineeringcondition to a reader positioned outside of the tire; the tire having asidewall that is an oriented attenuating body for the monitoring device;the oriented attenuating body having maximum and minimum attenuatinglevels; the non-attached monitoring device being loosely disposed withinthe tire; the monitoring device including a monitoring assembly and anantenna; wherein the improvement comprises: the antenna having anorientation that radiates a transmission pattern; the transmissionpattern having a portion that is attenuated by the oriented attenuatingbody of the tire sidewall at the minimum attenuating level regardless ofthe orientation of the monitoring device with respect to the tiresidewall.
 2. The improvement of claim 1, wherein the antenna includes anantenna body that is looped back 180 degrees on itself.
 3. Theimprovement of claim 2, wherein the monitoring assembly defines theground plane of the antenna; the body of the antenna being disposed in areference plane that is perpendicular to the ground plane.
 4. Theimprovement of claim 2, wherein the monitoring assembly defines theground plane of the antenna; the body of the antenna being disposed in areference plane that is parallel to the ground plane.
 5. The improvementof claim 2, wherein the monitoring assembly defines the ground plane ofthe antenna; the body of the antenna being disposed in a reference planethat is disposed at an angle between zero and 90 degrees to the groundplane.
 6. The improvement of claim 1, wherein the monitoring deviceincludes an antenna ground plane; the body of the antenna being disposedin a reference plane that is perpendicular to the ground plane.
 7. Theimprovement of claim 1, wherein the monitoring device includes antennaground plane; the body of the antenna being disposed in a referenceplane that is parallel to the ground plane.
 8. The improvement of claim1, wherein the monitoring device includes antenna ground plane; the bodyof the antenna being disposed in a reference plane that is disposed atan angle between zero and 90 degrees to the ground plane.
 9. Theimprovement of claim 1, wherein the monitoring assembly and antenna areencapsulated within a rigid encapsulation layer.
 10. The improvement ofclaim 1, wherein the antenna includes a pair of spaced, parallelconductive surfaces.
 11. The improvement of claim 10, wherein themonitoring device has a body that defines an outer surface; each of theconductive surfaces extending to the outer surface of the body of themonitoring device to define a slot.
 12. The improvement of claim 10,wherein one of the conductive surfaces is electrically connected to themonitoring assembly.
 13. The improvement of claim 12, wherein each ofthe conductive bodies is disc-shaped and has a center; the monitoringassembly being electrically connected to the conductive body at thecenter of the conductive body.
 14. The improvement of claim 1, whereinthe monitoring device has a body that defines an outer surface; theantenna including a pair of spaced conductive bodies that extend to theouter surface of the body to define a slot.
 15. The improvement of claim14, wherein the slot has a serpentine pattern.
 16. The improvement ofclaim 15, wherein one of the conductive surfaces is electricallyconnected to the monitoring assembly.
 17. The improvement of claim 1,wherein the antenna includes four spaced conductive bodies; each of thefour conductive bodies having first and second planar leg portions withcurved outer edges; the first planar leg portion being disposedperpendicular to the second planar leg portion.
 18. The improvement ofclaim 17, wherein the monitoring assembly is electrically connected totwo of the conductive bodies.